543 CHEMICAL ANALYSIS OF THE BRAIN. 



the tracing of the fibres through that organ, a matter of extreme 

 difficulty. 



But the existence of the neurilema there is nevertheless evi- 

 dent, and especially, as I have several times had occasion to 

 observe in cases of atrophy of parts of the brain, where the 

 nervous substance had disappeared, and the neurilema been left, 

 forming a shrunken mould ofthe part. 



In the sympathetic nervous system, there is, according to 

 Remak, a mixture of white and gray fibres, constituting the 

 trunks of the nerves. The primitive gray fibres, originate from 

 the sympathetic ganglia, are about one half the diameter of the 

 corresponding white fibres, and have their surface here and there 

 beset with minute granules of gray matter. The white fibres 

 which are seen in the sympathetic nerves intermixed with the 

 gray, especially in the neck, the loins, and the splanchnic nerves, 

 are believed to be additional sensitive, and perhaps excito-rnotor 

 nerves extending into them from the cerebro-spinal system. 

 Some of the cerebro-spinal nerves, as the trigeminus and 

 glosso-pharyngeal, contain some gray fibres of a similar sort, 

 which are derived from the sympathetic, and intermixed with 

 those coming from the brain. 



Mr. Johns* is the only chemist who, in his analysis of the 

 brain, has hitherto separately examined the gray and white mat- 

 ter. He has stated that the white matter contains more fat than 

 the gray, and that its albumen is more firm. The following 

 comparative analysis was made of the brain of one of the insane 

 patients who died at the Salpetriere. 



Entire Brain, (Density 1048.) 



Water, 77.0 



Albumen, - - 9.6 



White fatty matter, - 7.2 



Red fatty matter, - 3.1 



Osmazome, lactic acid, salts, - 2.0 



Earthy phosphate, - 1.1 



* Journal de Chimie Med. 1835 j Solly on the brain, p. 8. London, 1836. 



